/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.jni;

/**
 * Lock
 * 
 * @author Mladen Turk
 * @version $Revision: 467222 $, $Date: 2006-10-24 11:17:11 +0800 (星期二, 24 十月
 *          2006) $
 */

public class Lock {

	/**
	 * Enumerated potential types for APR process locking methods <br />
	 * <b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the
	 * platform supports APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.
	 */

	public static final int APR_LOCK_FCNTL = 0;
	/** fcntl() */
	public static final int APR_LOCK_FLOCK = 1;
	/** flock() */
	public static final int APR_LOCK_SYSVSEM = 2;
	/** System V Semaphores */
	public static final int APR_LOCK_PROC_PTHREAD = 3;
	/** POSIX pthread process-based locking */
	public static final int APR_LOCK_POSIXSEM = 4;
	/** POSIX semaphore process-based locking */
	public static final int APR_LOCK_DEFAULT = 5;

	/** Use the default process lock */

	/**
	 * Create and initialize a mutex that can be used to synchronize processes.
	 * <br />
	 * <b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the
	 * platform supports APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.
	 * 
	 * @param fname
	 *            A file name to use if the lock mechanism requires one. This
	 *            argument should always be provided. The lock code itself will
	 *            determine if it should be used.
	 * @param mech
	 *            The mechanism to use for the interprocess lock, if any; one of
	 * 
	 * <PRE>
	 *            APR_LOCK_FCNTL
	 *            APR_LOCK_FLOCK
	 *            APR_LOCK_SYSVSEM
	 *            APR_LOCK_POSIXSEM
	 *            APR_LOCK_PROC_PTHREAD
	 *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
	 * </PRE>
	 * 
	 * @param pool
	 *            the pool from which to allocate the mutex.
	 * @return Newly created mutex.
	 */
	public static native long create(String fname, int mech, long pool)
			throws Error;

	/**
	 * Re-open a mutex in a child process. This function must be called to
	 * maintain portability, even if the underlying lock mechanism does not
	 * require it.
	 * 
	 * @param fname
	 *            A file name to use if the mutex mechanism requires one. This
	 *            argument should always be provided. The mutex code itself will
	 *            determine if it should be used. This filename should be the
	 *            same one that was passed to apr_proc_mutex_create().
	 * @param pool
	 *            The pool to operate on.
	 * @return Newly opened mutex.
	 */
	public static native long childInit(String fname, long pool) throws Error;

	/**
	 * Acquire the lock for the given mutex. If the mutex is already locked, the
	 * current thread will be put to sleep until the lock becomes available.
	 * 
	 * @param mutex
	 *            the mutex on which to acquire the lock.
	 */
	public static native int lock(long mutex);

	/**
	 * Attempt to acquire the lock for the given mutex. If the mutex has already
	 * been acquired, the call returns immediately with APR_EBUSY. Note: it is
	 * important that the APR_STATUS_IS_EBUSY(s) macro be used to determine if
	 * the return value was APR_EBUSY, for portability reasons.
	 * 
	 * @param mutex
	 *            the mutex on which to attempt the lock acquiring.
	 */
	public static native int trylock(long mutex);

	/**
	 * Release the lock for the given mutex.
	 * 
	 * @param mutex
	 *            the mutex from which to release the lock.
	 */
	public static native int unlock(long mutex);

	/**
	 * Destroy the mutex and free the memory associated with the lock.
	 * 
	 * @param mutex
	 *            the mutex to destroy.
	 */
	public static native int destroy(long mutex);

	/**
	 * Return the name of the lockfile for the mutex, or NULL if the mutex
	 * doesn't use a lock file
	 */
	public static native String lockfile(long mutex);

	/**
	 * Display the name of the mutex, as it relates to the actual method used.
	 * This matches the valid options for Apache's AcceptMutex directive
	 * 
	 * @param mutex
	 *            the name of the mutex
	 */
	public static native String name(long mutex);

	/**
	 * Display the name of the default mutex: APR_LOCK_DEFAULT
	 */
	public static native String defname();

}
